March Madness is all about the upset: David taking down Goliath and shocking the world. But since the NCAA Tournament expanded to 64 teams in 1985, a No. 16 seed has never defeated a No. 1 seed, going 0-128. According to FiveThirtyEight probability data, we should have seen three 16 vs. 1 upsets by now. There have been some close calls, but why hasn’t it happened yet? What are the odds and determining factors? Will we ever see The Ultimate Upset?